12-15-2008, 09:56 PM
A 27-year-old man has a 3-week history of fever, headache, malaise, decreased appetite, a dry cough, and a 1.3-kg (3-lb) weight loss. His symptoms began 1 week after a 1-month trip to help construct homes in rural Mexico. Seven or eight members of the construction group have developed similar symptoms. The patient's medical history is unremarkable.
On physical examination, temperature is 37.4 °C (99.3 °F), pulse rate is 74/min, respiration rate is 20/min, and blood pressure is 142/88 mm Hg. The head, eyes, ears, nose, and throat are normal. Diffuse crackles are heard throughout all lung fields. Cardiac, abdominal, and neurologic examinations are normal. The extremities are normal.
Laboratory Studies
Hemoglobin
14.5 g/dL (145 g/L)
Hematocrit
44%
Leukocyte count
9200/μL (9.2 × 109/L)
Platelet count
325,000/μL (325 × 109/L)
Blood urea nitrogen
18 mg/dL (6.43 mmol/L)
Serum creatinine
1.0 mg/dL (88.42 µmol/L)
Serum electrolytes
Normal
Serum aspartate aminotransferase
71 U/L
Serum alanine aminotransferase
95 U/L
Serum total bilirubin
0.9 mg/dL (15.39 µmol/L)
Urinalysis
Normal
A chest radiograph shows diffuse reticulonodular infiltrates throughout both lung fields with enlarged mediastinal lymph nodes. CT-guided lung biopsy samples demonstrate early granulomatous inflammation; stains for bacteria, mycobacteria, and fungi are negative.
Which of the following pathogens is most likely causing this patient's findings?
A Mycobacterium tuberculosis
B Aspergillus fumigatus
C Staphylococcus aureus
] D Histoplasma capsulatum
On physical examination, temperature is 37.4 °C (99.3 °F), pulse rate is 74/min, respiration rate is 20/min, and blood pressure is 142/88 mm Hg. The head, eyes, ears, nose, and throat are normal. Diffuse crackles are heard throughout all lung fields. Cardiac, abdominal, and neurologic examinations are normal. The extremities are normal.
Laboratory Studies
Hemoglobin
14.5 g/dL (145 g/L)
Hematocrit
44%
Leukocyte count
9200/μL (9.2 × 109/L)
Platelet count
325,000/μL (325 × 109/L)
Blood urea nitrogen
18 mg/dL (6.43 mmol/L)
Serum creatinine
1.0 mg/dL (88.42 µmol/L)
Serum electrolytes
Normal
Serum aspartate aminotransferase
71 U/L
Serum alanine aminotransferase
95 U/L
Serum total bilirubin
0.9 mg/dL (15.39 µmol/L)
Urinalysis
Normal
A chest radiograph shows diffuse reticulonodular infiltrates throughout both lung fields with enlarged mediastinal lymph nodes. CT-guided lung biopsy samples demonstrate early granulomatous inflammation; stains for bacteria, mycobacteria, and fungi are negative.
Which of the following pathogens is most likely causing this patient's findings?
A Mycobacterium tuberculosis
B Aspergillus fumigatus
C Staphylococcus aureus
] D Histoplasma capsulatum